The initiation of DNA replication at replication origins is essential for the duplication of genomes. In yeast, the autonomously replicating sequence (ARS) property of replication origins is necessary for the stable maintenance of episomal plasmids. However, because the sequence determinants of ARS function differ among yeast species, current ARS modules are limited for use to a subset of yeasts. In addition, lower efficiency replication origins result in the loss of plasmids during culture growth. Origins have not been isolated or optimized in many yeast species, making the use of plasmid-based expression systems difficult.
Due to the diversity of sequences required for origin function in different yeast species, ARSs are usually restricted to function in only a few yeast species. For example, K. lactis ARSs rarely work in non-Kluyveromyces yeasts and ARSs from other species rarely function in K. lactis host cells (Liachko et al. 2010; 2011). On the other hand, L. kluyveri is a permissive host species and can utilize most ARSs from S. cerevisiae and K. lactis (Liachko et al. 2011). The methylotrophic budding yeast Pichia pastoris uses at least two different kinds of ARS sequences, neither of which function in S. cerevisiae (Liachko et. al., PLoS Genetics, 2014, in press).
There remains a need for an ARS that functions across all yeasts. In addition to facilitating commercial use of yeast expression systems, an ARS that works across a variety of yeast species would be a useful genetic tool to provide shuttle vectors for cross-species studies.